Voltage conversion circuit and power supply system

Abstract

A voltage conversion circuit includes: an inductor, a first switch module, N second switch modules connected in series, N third switch modules connected in series, and N−1 flying capacitors. One terminal of the first switch module is separately connected to one terminal of the N second switch modules connected in series and one terminal of the N third switch modules connected in series. The other terminal of the N third switch modules connected in series is connected to a positive electrode of a high-voltage power supply. The other terminal of the first switch module and the other terminal of the N second switch modules connected in series are connected to a negative electrode of the high-voltage power supply. A low-voltage power supply is connected to the two terminals of the first switch module through the inductor.

What is claimed is: 
     
       1. A voltage conversion circuit, comprising:
 an inductor; 
 a first switch module; 
 N second switch modules connected in series; 
 N third switch modules connected in series; and 
 N−1 flying capacitors, wherein N is an integer greater than or equal to 2; 
 wherein one terminal of the first switch module is separately connected to one terminal of the N second switch modules connected in series and one terminal of the N third switch modules connected in series, the other terminal of the N third switch modules connected in series is connected to a positive electrode of a high-voltage power supply, the other terminal of the first switch module and the other terminal of the N second switch modules connected in series are connected to a negative electrode of the high-voltage power supply, and a low-voltage power supply is connected to the two terminals of the first switch module through the inductor; 
 wherein one terminal of an i th  flying capacitor in the N−1 flying capacitors is connected to a connection point between an i th  second switch module and an (i+1) th  second switch module, the other terminal of the i th  flying capacitor is connected to a connection point between an i th  third switch module and an (i+1) th  third switch module, and i is an integer greater than or equal to 1 and less than or equal to N−1; 
 wherein in one switching period, the circuit performs boost conversion on a voltage output by the low-voltage power supply, by using at least one flying capacitor charging mode and a boost discharging mode; and 
 wherein at least one flying capacitor comprises a plurality of flying capacitors, the plurality of flying capacitors are connected in parallel in each flying capacitor charging mode and the boost discharging mode. 
 
     
     
       2. The circuit according to  claim 1 , wherein a positive electrode of the low-voltage power supply is connected to one terminal of the first switch module through the inductor, and a negative electrode of the low-voltage power supply is connected to the other terminal of the first switch module. 
     
     
       3. The circuit according to  claim 1 , wherein the inductor is located in between a negative electrode of the low-voltage power supply and one end of the first switch module, and a positive electrode of the low-voltage power supply is connected to the other end of the first switch module. 
     
     
       4. The circuit according to  claim 1 , wherein in the one switching period, the circuit performs, by further using an inductor charging mode, the boost conversion on the voltage output by the low-voltage power supply,
 wherein 
 in the inductor charging mode, the low-voltage power supply and the inductor form a closed loop, to charge the inductor; 
 wherein in each flying capacitor charging mode, the low-voltage power supply, the inductor, and the at least one flying capacitor in the N−1 flying capacitors form a closed loop, to charge the at least one flying capacitor; and 
 wherein in the boost discharging mode, the low-voltage power supply, the inductor, one or more flying capacitors in the at least one flying capacitor, and the high-voltage power supply form a closed loop, to discharge the high-voltage power supply. 
 
     
     
       5. The circuit according to  claim 4 , wherein each operation mode occurs at least once in one switching period. 
     
     
       6. The circuit according to  claim 5 , wherein each flying capacitor charging mode is used to charge the at least one flying capacitor in the N−1 flying capacitors; and
 in the boost discharging mode, the low-voltage power supply, the inductor, the at least one flying capacitor, and the high-voltage power supply form a closed loop, to discharge the high-voltage power supply. 
 
     
     
       7. The circuit according to  claim 6 , wherein a quantity of flying capacitors in the at least one flying capacitor is positively correlated with a magnitude of a current output by the low-voltage power supply. 
     
     
       8. The circuit according to  claim 5 , wherein capacitance values of the N−1 flying capacitors are increased stage by stage;
 wherein the one switching period comprises a plurality of flying capacitor charging modes, the plurality of flying capacitor charging modes are used to charge a plurality of flying capacitors in the N−1 flying capacitors stage by stage, and each flying capacitor charging mode is used to charge one flying capacitor in the plurality of flying capacitors; and 
 wherein in the boost discharging mode, the low-voltage power supply, the inductor, a last-stage flying capacitor in the plurality of flying capacitors, and the high-voltage power supply form a closed loop, to discharge the high-voltage power supply. 
 
     
     
       9. The circuit according to  claim 8 , wherein a quantity of the plurality of flying capacitors is in relation to a boost ratio of the voltage conversion circuit. 
     
     
       10. A voltage conversion circuit, comprising:
 an inductor; 
 a first switch module; 
 two second switch modules connected in series; 
 two third switch modules connected in series; and 
 a flying capacitor, wherein 
 one terminal of the first switch module is separately connected to one terminal of the two second switch modules connected in series and one terminal of the two third switch modules connected in series, the other terminal of the two third switch modules connected in series is connected to a positive electrode of a high-voltage power supply, the other terminal of the first switch module and the other terminal of the two second switch modules connected in series are connected to a negative electrode of the high-voltage power supply, and a low-voltage power supply is connected to the two terminals of the first switch module through the inductor; 
 wherein one terminal of the flying capacitor is connected to a connection point between a first second switch module and a second switch module, and the other terminal of the flying capacitor is connected to a connection point between a first third switch module and a second third switch module; 
 wherein in one switching period, the circuit performs boost conversion on a voltage output by the low-voltage power supply, by using at least one flying capacitor charging mode and a boost discharging mode; and 
 wherein at least one flying capacitor comprises a plurality of flying capacitors, the plurality of flying capacitors are connected in parallel in each flying capacitor charging mode and the boost discharging mode. 
 
     
     
       11. The circuit according to  claim 10 , wherein a positive electrode of the low-voltage power supply is connected to one terminal of the first switch module through the inductor, and a negative electrode of the low-voltage power supply is connected to the other terminal of the first switch module. 
     
     
       12. The circuit according to  claim 10 , wherein the inductor is located in between a negative electrode of the low-voltage power supply and one end of the first switch module, and a positive electrode of the low-voltage power supply is connected to the other end of the first switch module. 
     
     
       13. The circuit according to  claim 10 , wherein in the one switching period, the circuit performs, by further using an inductor charging mode, boost conversion on a voltage output by the low-voltage power supply:
 wherein 
 in the inductor charging mode, the low-voltage power supply and the inductor form a closed loop, to charge the inductor; 
 wherein in each flying capacitor charging mode, the low-voltage power supply, the inductor, and the at least one flying capacitor in the N−1 flying capacitors form a closed loop, to charge the at least one flying capacitor; and 
 wherein in the boost discharging mode, the low-voltage power supply, the inductor, one or more flying capacitors in the at least one flying capacitor, and the high-voltage power supply form a closed loop, to discharge the high-voltage power supply. 
 
     
     
       14. The circuit according to  claim 13 , wherein each operation mode occurs at least once in one switching period. 
     
     
       15. The circuit according to  claim 14 , wherein each flying capacitor charging mode is used to charge the at least one flying capacitor in the N−1 flying capacitors; and
 in the boost discharging mode, the low-voltage power supply, the inductor, the at least one flying capacitor, and the high-voltage power supply form a closed loop, to discharge the high-voltage power supply. 
 
     
     
       16. A power supply system, comprising:
 a plurality of power generation units; and 
 a high-voltage power supply, and 
 wherein each power generation unit comprises a low-voltage power supply and a voltage conversion circuit, wherein the voltage conversion circuit comprises an inductor, a first switch module, N second switch modules connected in series, N third switch modules connected in series, and N−1 flying capacitors, wherein N is an integer greater than or equal to 2; 
 wherein one terminal of the first switch module is separately connected to one terminal of the N second switch modules connected in series and one terminal of the N third switch modules connected in series, the other terminal of the N third switch modules connected in series is connected to a positive electrode of a high-voltage power supply, the other terminal of the first switch module and the other terminal of the N second switch modules connected in series are connected to a negative electrode of the high-voltage power supply, and a low-voltage power supply is connected to the two terminals of the first switch module through the inductor; 
 wherein one terminal of an i th  flying capacitor in the N−1 flying capacitors is connected to a connection point between an i th  second switch module and an (i+1) th  second switch module, the other terminal of the i th  flying capacitor is connected to a connection point between an i th  third switch module and an (i+1) th  third switch module, and i is an integer greater than or equal to 1 and less than or equal to N−1; 
 wherein in one switching period, the circuit performs boost conversion on a voltage output by the low-voltage power supply, by using at least one flying capacitor charging mode and a boost discharging mode; and 
 wherein at least one flying capacitor comprises a plurality of flying capacitors, the plurality of flying capacitors are connected in parallel in each flying capacitor charging mode and the boost discharging mode. 
 
     
     
       17. The system according to  claim 16 , wherein a positive electrode of the low-voltage power supply is connected to one terminal of the first switch module through the inductor, and a negative electrode of the low-voltage power supply is connected to the other terminal of the first switch module. 
     
     
       18. The system according to  claim 16 , wherein the inductor is located in between a negative electrode of the low-voltage power supply and one end of the first switch module, and a positive electrode of the low-voltage power supply is connected to the other end of the first switch module. 
     
     
       19. The system according to  claim 16 , wherein the low-voltage power supply is a photovoltaic string, and the high-voltage power supply is a direct current bus; and the power supply system further comprises an inverter, wherein
 a positive electrode of the direct current bus is connected to a first input terminal of the inverter, a negative electrode of the direct current bus is connected to a second input terminal of the inverter, and an output terminal of the inverter is connected to an alternating current load. 
 
     
     
       20. The system according to  claim 16 , wherein the low-voltage power supply is a photovoltaic string, and the high-voltage power supply is a direct current load.